The conventional illuminating devices, e.g., light-emitting diode (LED) lamps, are more and more popular due to the advantages of energy saving, environmental protection and long service life, and may be applied in office, home and other occasions. In order to widen the indoor lighting area, or to meet the needs of indoor lighting in different locations, or to meet the interior decoration effect, an LED lamp may include a plurality of LED linear lamps and a plurality of adapters for connecting two adjacent LED linear lamps in the plurality of LED linear lamps. The linear lamp adapter sometimes is usually made from opaque plastics. When two LED linear lamps are connected, an adapter is required to connect them. Although the overall lighting area of the LED lamp is enlarged, due to the arrangement of the adapters, dark areas will be produced between the LED linear lamps, so continuous linear lighting cannot be realized, and meanwhile, the aesthetic property and the decorative effect of the lamp may also be affected.